1. Field of the Invention
The present invention relates to milling cutters and cutting inserts used thereon, and in particular to a true helical cutter system that includes a milling cutter with true helical indexable cutting inserts that creates a continuous true helical cut.
2. Description of the Related Art
One of the current concerns in milling is the stepped or wavy surface on the milled surface, specifically in the areas of face and end milling. This stepped, uneven or otherwise irregular finish is typically a result of the type, position and location of the cutting inserts. This stepping is particularly relevant in attempts at all-in-one mills, that is mills capable of three dimensional milling, including plunging, ramping, circle interpolating, facing, and end milling with the same mill.
Cutting inserts that are not properly aligned along the flutes of the mill will provide such stepping. For example, on helical mills the inserts must be aligned to follow the curved contour of the helix and any misalignment results in stepping or other irregular finish such as a groove or lip where one insert is radially outward further than adjacent inserts. In addition, cutting inserts that have substantially rectangular configurations (that is, with long, flat cutting edges) will provide such stepping. This stepping is caused by the rectangular configuration of the insert removing excessive material from the workpiece at or approaching the corners of the inserts thereby causing stepping. In contrast, cutting inserts that have an arc-like periphery along its entire cutting surface (radiused corners that extend across the whole cutting edge) remove excess material from the workpiece along the mid-section of the cutting insert, thereby causing valleys.
It is believed that this stepped surface is often unacceptable, particularly when a finished, as opposed to a rough surface is desired. This stepping is unacceptable because stress points typically form at the inner and outer edges of the steps as these edges are often well defined. This forces the milling user to thereafter finish mill the surface that is an additional time consuming and expense-adding step.
Such improvement in milling continues to be sought in various industries because such reduction or complete elimination of all stepping and waviness will increase the overall life of the metal end product by reducing and/or eliminating stress, fatigue and other undesirable forces working against the metal end product. In conjunction with this, if a milling cutter could perform all or substantially all of the typical milling steps including ramping, plunging, circle interpolation, facing and end milling, then significant cost and time reduction would also be achieved. Finally, if all such milling steps could be achieved by one milling cutter, it is desirable that the milling cutter still have a reasonable life even though these various steps involve different concerns and factors including the subjecting of the cutter to large axial, radial, and tangential forces, possibly simultaneously.
The inventor of the present invention has recognized these and other problems and has developed a true helix cutting system in which the helically arranged cutting inserts provide a true helical cutting edge to the workpiece, resulting in an improved cutting action that reduces or completely eliminates all stepping and waviness in the workpiece.
The present invention relates to an improved milling cutting system that is designed to create a continuous cutting true helix while having true helical inserts that are indexable on two cutting edges by rotating the insert by 180 degrees.
The present invention comprises a true helical cutter system that includes a milling body having a plurality of mounting pockets and a plurality of cutting inserts mounted to the mounting pockets of the milling body. Each cutting insert includes front and back faces, at least two opposing side walls, at least one cutting edge defined at an intersection between the front face and the combination of one of the side walls, wherein the front face of each insert is radiused to create a true helical insert.
In one aspect of the invention, at least one of the side walls of each insert includes a notched face for allowing each of the cutting inserts that are grouped into a helically attached group to interlock with one another.
In another aspect of the invention, at least one of the side walls of each insert include a helical cut face to form a side face helix that creates a smooth cutting action as a solid helical end mill.
Various aspects and advantages of this invention will become apparent to those skilled in the art from the following detailed description of the preferred embodiment, when read in light of the accompanying drawings.